/*
 * @Author: Dagon
 * @Date: 2021-03-18 09:41:04
 * @Description: 闭包使用
 */
function add (n) {
  var num = n;
  return function addTo(x) {
    return x + num;
  }
}

addTwo = add(2)
// console.log(addTwo(5))

const a = undefined;
console.log(a + 4)